Monolithic ICs generally comprise a number of transistors, such as metal-oxide-semiconductor field-effect transistors (MOSFETs) fabricated over a planar substrate, such as a silicon wafer.
ICs often include at least one antifuse. An antifuse is an electrical device that starts with a high resistance and is designed to permanently create a conductive path when the voltage across the device exceeds a threshold level. With transistor dimension scaling from one generation to another, it is advantageous to scale down the antifuse program voltage.
MOS antifuse designs often employ a MOS transistor-based structure, as depicted in FIG. 1A. MOS antifuse 10 disposed on substrate 5 employs a gate electrode 13 and a source/drain contacts 14 surrounded by an isolation dielectric 15. With gate electrode 13 biased up to a programming voltage and source/drain contacts 14 held at a reference potential (e.g. ground), the antifuse program circuit path passes through a gate dielectric 11, a nominally doped semiconductor well or fin 8, and heavily doped semiconductor source/drain 9. Formation of a conductive path during a programming operation entails permanently breaking down gate dielectric 11, which changes the resistance between gate electrode 13 and source/drain contacts 14. If gate dielectric 11 is intact, antifuse 10 displays normal MOSFET characteristics. If gate dielectric 11 experiences dielectric breakdown, antifuse 10 will not have normal MOSFET characteristics and instead have an associated programmed antifuse resistance.
MOS antifuse architectures and associated fabrication techniques that offer lower antifuse program voltages are advantageous.